The present invention relates to a technology of recording and/or reproducing of an optical information, with which an information can be written or erased on an information recording medium by irradiating a light thereupon.
Conventionally, the optical information recording and/or reproducing (recording/reproducing) apparatuses of various methods are already known and actually practiced in products, in which an information is optically read out from a disc-like information recording medium, on which the information is recorded by use of a phase change being reversibly changeable between a crystal state and an amorphous state, being different in reflectivity to each other, so as to be reproduced. Also, in particular in recent years, as an information recording medium being able to record a large amount of information thereon, with increasing the recording density of the information, for example, a one being called by a DVD-RAM (Digital Versatile Disc-Random Access Memory) disc was proposed and attracts attentions thereto. And, also an optical information recording/reproducing apparatuses was already on the market, which can perform the recording and reproducing of the information on and from such the DVD-RAM disc.
As an aspect to be paid attentions when writing or erasing the information on the information recording medium being recordable with information, there is a phenomenon which is called by xe2x80x9coff trackxe2x80x9d. The off track means a phenomenon, in which an optical spot formed on a recording surface of the optical disc comes to be off from a track to be scanned or traced inherently, due to the external factors, such as vibration of the apparatus or the like, and the internal factors, such as an abnormal function of a tracking controller circuit for scanning or tracking it around a center of the track or the like, and further other factors of the optical disc itself, such as, scratches, dirt, defects on the optical disc surface, etc.
If the off track occurs during the writing or erasing of the information, since it occasionally erases the information on other track(s) erroneously, therefore it is necessary to watch whether the off track occurs or not always, so as to stop the write or erase operation when it actually occurs.
In the optical information recording/reproducing apparatus, the phenomenon of this off track is detected with such the construction as shown in FIG. 6. Hereinafter, explanation will be given on the optical information recording/reproducing apparatus which can detects the off track, by referring to the FIG. 6. This figure is a block diagram for showing the construction which is necessary for the detection of the off track in the optical information recording/reproducing apparatus, therefore other portion or construction thereof is omitted to be shown here.
An optical disc 101 is rotated by a spindle motor 102, and on a recording surface of the optical disc 101 is irradiated a laser beam from an optical head or pickup 103 to be formed as an optical spot on it. Then a reflection light of the laser beam irradiated upon the optical disc 101 is detected by the optical head (pickup) 103, so as to form various signals depending upon the level of the reflection light therefrom. Among the signals formed, a signal called by a tracking error signal (i.e., a TE signal) to be used for a tracking control, indicating an amount of fluctuation with respect to a center of the track, is determined whether it exceeds a comparison (or reference) level or not in the level thereof (i.e., the voltage) by means of a comparator 104, so as to output a signal, which turns to a high level during when it exceeds the comparison level while a low level during when it does not. A time counting device 105 (i.e., pulse width detector) measures or counts up the time length during when the signal outputted from the comparator 104 is at the high level. If the time duration of the output exceeds a predetermined time period, since there is a possibility that the optical spot may or has already come off erroneously into other track, then a signal is outputted to an OR circuit 109.
While, since it is possible to read out an information of bits which are formed on a PID portion of the optical disc 101 from the TE signal, the TE signal is decoded in a PID decoder 106, so as to read out the information therefrom. In the pit information of the PID portion is contained a position or location information on the track, therefore it can be acknowledged on which track the optical spot is tracking or scanning at present. /Also, in a PID register 107 is memorized an order of the location information on the track, before performing the recording and/or reproducing of the information in advance. Then, a comparator 108 receives the location information of the PID portion 107 which will be read out from the optical disc next, and compares this information with the location information of the PID portion which is actually read out by the PID decoder 106. If the result of the comparison is inconsistent with, it can be acknowledged that the optical spot comes off into other track erroneously, therefore a signal is outputted to the OR circuit 109.
And, the OR circuit 109 outputs a stop signal of write or erase when the signal is inputted from the time counting device 105 or the comparator 108, thereby to stop the operation of write or erase of the information by the optical information recording/reproducing apparatus.
With such the conventional optical information recording/reproducing apparatus as mentioned in the above, however, if the comparison level is set to be low in the comparator 104 so as to set the period of the time counting device 105 (i.e., pulse width detector) short, there is a margin in relation to the detection on the off track phenomenon, therefore it can detects both, an abrupt change and a slow change in the position where the optical spot is formed. However, there is still a possibility that the signal is outputted from the time counting device 105 (i.e., pulse width detector) even upon a small fluctuation in the TE signal, such as a noise component(s) of the TE signal, thereby stopping the operation of write or erase in spite of no occurrence of the off track.
On the other hand, if the comparison level is set to be high in the comparator 104 so as to set the period of the time counting device 105 (i.e., pulse width detector) long, there is no margin in relation to the detection on the of f track phenomenon, therefore it cannot detect the abrupt change of the position where the optical spot is irradiated, in a radial direction thereof, thereby bringing about a possibility that the write or erase of the information is performed on other track.
Further, for detecting the off track phenomenon from the comparison result by means of the comparator 108, there is a necessity to read out the information of the PID portion. Saying contrary to this, it is impossible to detect the off track phenomenon not so far as the information of the PID portion can be read out, therefore there is a possibility that the write or erase of the information has been already done on other track at the time point when the off track is detected if the off tack occurred before reading out of the information of the PID portion.
An object according to the present invention is, for dissolving such the problems, to provide an optical information recording/reproducing apparatus, with which the possibility of performing the operation of write or erase of an information on other track(s), and also the possibility of the erroneous detection of the phenomenon of the off track can be reduced.
According to the present invention, for dissolving the above-mentioned object, there is provided an optical information recording/reproducing apparatus for performing an operation of write or erase of information on an optical disc, comprising:
means for irradiating an optical spot on said optical disc;
means for controlling fluctuation in position of said optical spot, with respect to a track center on said optical disc, in a radial direction thereof;
a first means for stopping the operation of the write or erase of information, if the fluctuation in position of said optical spot in the radial direction is equal or more than a first fluctuation amount and if a time period during when the positional fluctuation is equal or more than the first fluctuation amount is equal or longer than a first time period; and
a second means for stopping the operation of the write or erase of information, if the fluctuation in position of said optical spot in the radial direction is equal or more than a second fluctuation amount and if a fluctuation time period during when the positional fluctuation is equal or more than the second fluctuation amount is equal or longer than a second time period.